We report the synthesis, structural characterization, oxide ion and proton conductivities of the perovskite-related Ba3–xSrxYGa2O7.5 family. Single-phase samples are prepared for 0 x 3 and show a complex structural evolution from P2/c to C2 space groups with increasing x. For 1.0 ≲ x ≲ 2.4 average structures determined by X-ray and neutron powder diffrac-tion show metrically orthorhombic unit cells, but HAADF-STEM imaging reveals this is caused by microstructural effects due to intergrowths of the Ba- and Sr-rich structure types. Variable temperature powder diffraction studies suggest that compositions with 0 ≲ x ≲ 2.4 undergo a phase transition on heating to space group Cmcm that involves disordering of the oxygen substructure. Thermal expansion coefficients are reported for the series. Complex impedance studies show that the Ba-rich samples are mixed proton and oxide ion conductors under moist atmospheres, but are predominantly oxide ion conductors at high temperature or under dry atmospheres. Sr-rich samples show significantly less water uptake and appear to be predominantly oxide ion conductors under the conditions studied.
Fuller, C. A., Murrell, J. I., Blom, D. A., Vogt, T., Zhang, W., Halasyamani, P. S., …Evans, J. S. (2022). Oxide ion conductivity, proton conductivity and phase transitions in perovskite-derived Ba3–xSrxYGa2O7.5 0 x 3 materials. Chemistry of Materials, 34(7), 3185-3196. https://doi.org/10.1021/acs.chemmater.1c04372